Popular Plasma

Massless Speakers Part 4

Plasma tweeters of the 70's, Corona Acoustic and Hill Plasmatronic
Not one you can hear

A previous reseller of the Ionovac in Germany, Otto Braun, created an updated plasma tweeter in 1978.  His company Corona Acoustic developed the Corona type 314-514.  Again a slight misnomer as this was a plasma tweeter and not a corona based speaker, but close.  It is similar to the Ionovac in that a plasma is created in a quartz tube which is horn loaded and driven by local circuitry at the rear.  Their description of its operation differs from what may be found here for plasma tweeters as it doesn't include any thermal characteristics in the explanation, it is described more closely to an ion wind speaker.  That doesn't quite fit but we can agree to disagree as these devices are difficult to classify.

Lansche Corona
A Lansche Audio plasma
This plasma tweeter has had one of the longest lifespans of any massless speaker as the production of it was taken over in 1998 by Lansche Audio who still sells it.  Acapella (formerly ATR) have a very similar current model which was the Ion-TW-1 and is now only sold in their high end loudspeaker systems.  None of these appear to have obtained patents or had to license their designs, which would make sense from the amount of prior art.

Around the same time as the Corona was created, in 1979 the Hill Plasmatronic was made in the US and patented at the same time.  This well known commercial product was a full range speaker system using a unique plasma tweeter based on a DC bias system instead of RF and with several plasmas rather than being horn loaded.  Notorius for its use of helium tanks in the speaker cabinet, the helium was gently flowed into the plasma tweeter chamber preventing it from creating any noxious gases.  It seems that little attention was paid to this major negative issue of high voltage massless speakers until now.  Without some measures taken all types of plasma/ion/corona loudspeakers react with the air to create ozone and NOx.  These toxic gases are harmful, especially in closed rooms where concentrations can build to harmful levels.  By replacing the air locally with an inert gas no reaction can take place so no toxic gases are produced.

Hill Plasmatronic
Hill Plasmatronic Tweeter
The Plasmatronic was reviewed well in articles from Popular Science (1979), International Audio Review (1980) and Stereophile (1980) but with most mentioning how the large helium tanks may be a major downside.  It definately goes down as one of the best looking tweeters although the rest of the speaker cabinet was rather chunky and mundane.

Along with the Magnat mentioned previously the late 70's and early 80's could be seen as the hay-day of plasma tweeter commercial competition.

Part 5 - Don't Breathe
How Old?
Actual Plasma
A Stiff Breeze
Popular Plasma
Don't Breathe
Future Thinking

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